The use of chemical exfoliating agents such as alpha- and beta-hydroxy acids is associated with fresher, smoother-looking skin. The main function of these acids is to exfoliate the skin by weakening the bonds that hold the cells together in the skin's upper most layers, i.e., the stratum corneum. The overall effect is described as combating wrinkles, photoaging, and loss of smoothness and elasticity. The basis for the significant impact of alpha- and beta-hydroxy acids as skin treatments is their ability to reduce corneocyte adhesion and to accelerate cell proliferation within the basal layer of the stratum corneum. Continued use of these ingredients in topically applied compositions provides a gradual reduction in fine lines and an improvement in skin texture by virtue of accelerated desquamation.
Alpha-hydroxy acid compositions of the prior art may include fatty acid glycols, and surfactants and emulsifiers which may be silicon polymers, or humectants which may include functionalized silicone polymers. U.S. Pat. No. 5,000,945 combines organic acids with oils and sunscreens in fatty acid-based compositions which may have glycol surfactants. U.S. Pat. No. 5,244,665 includes citric acid triester monomeric compounds, polyethylene emulsifiers, and silicone emulsifier/surfactants. U.S. Pat. No. 5,439,682 is directed to a skin cleansing moisturizing composition including functionalized silicone polymers, as a dispersed insoluble oil phase, and hydroxy acid humectants.
Skin-care products which act against aging effects or which remove or lessen age-induced wrinkles are of increasing demand to consumers. Topically applied compositions having alpha- and beta-hydroxy acids such as lactic or glycol acids exhibit improved effects in relation to prior active ingredients asserted to reduce aging over a prolonged period of use. However, consumers may experience dissatisfaction if the desired effects are not readily perceived, or if they experience the undesirable side effects of topical compositions which may cause a stinging sensation as a result of the presence of the acids in the composition. Based on these difficulties, consumers may stop using the products altogether, or, in the case of stinging or burning sensations, may deter other potential users from trying the products. These problems may also lead to intermittent usage of such skin care products which then compromises the ultimate beneficial effects of long-term usage.
As such, there is a need in the art for a composition which enhances the performance of skin exfoliating agents such as hydroxy acids and which minimizes skin irritancy typically associated with their use.
In addition to attempts to reduce the effects of skin aging caused by natural aging processes, there is increased interest in protecting skin from the effects of the sun. With the ever-increasing rate of damage to the skin associated with exposure to UV radiation, including the risk of melanoma, consumers are looking for ways to guard the skin from sun exposure, such as by using various sunscreen-containing topically applied compositions. However, many consumers still seek to achieve the look of a tan or a "healthy" coloring to their skin without incurring the risks involved with actually tanning by harmful exposure to the sun's radiation. One way of achieving this affect cosmetically is to use compositions containing "sunless tanning" active ingredients. While sunless-tanning agents have been used for many years, they have not provided adequate tanning effects with respect to color, substantivity and harmlessness to the skin. The tanning mechanism consists of a Maillard reaction of dihydroxyacetone (DHA) with amines of the stratum corneum to yield brown polymeric structures on the skin. The molecule reacts with the skin in as short a time as three hours, providing a brown color which typically lasts for only up to a few days. Cosmetics manufacturers, as well as consumers of such products, desire a product which would enhance the color development and prolong the developed color.
While modem cosmetic products attempt to reduce the effects of aging and avoid exposure to the sun while providing enhanced coloring, as noted above, there is also a desire of many consumers to alter their existing skin appearance with respect to the effects of hyperpigmentation. Such effects may include dark patches, freckles or other skin pigmentation effects. Topically applied compositions are available to make skin appear lighter or to retard or inhibit pigmentation. Lightening may be achieved by applying pigmentation to the skin surface, by reducing the normal pigmentation process which continuously occurs, or by bleaching extracellular and relatively fixed pigment. Products associated with applying pigmentation to the skin surface, such as cosmetics, must be present on the skin surface continuously to achieve the effect of a lighter complexion. Cosmetics containing active ingredients which are designed to reduce the normal pigmentation process or which bleach extracellular pigment can be applied at definite intervals over a period of time. The overall effects of depigmentation are achieved by the mechanisms of either reducing pigmentation by decolorizing the melanin already present in the skin and/or by preventing new melanin from being formed. Products which can accelerate and improve these mechanisms are desired in the cosmetics industry.
In addition to the above cosmetic products which are in increasing demand, there is a need in the art for protective topical compositions which provide insect repellent capabilties for prolonged periods of time without causing detrimental harm to the user from penetration of the repellent. The increased incidence of mosquito- or other insect-borne health problems, such as encephalitis has heightened the public demand for such products. The most popular such repellent, which has been in use for many years, is N, N-dimethyl-m-toluamide (DEET). In order for DEET to be effective, however, it must remain on or in the outermost layers of human skin. Absorption of DEET through or deep into the epidermis of the user may sensitize the user to DEET's effect and render the use of the repellent incapable of performing its function. As such there is a need in the art to localize DEET in the outer stratum corneum or on top of the skin to enhance its effectiveness and to avoid sensitizing users to DEET's harmful side effects.
Applicants previously investigated the effects of various end-functionalized polyesters in general for use in hair and skin personal care products. The results of this investigation and early experimentation are set forth in WO 96/06878, the entire teaching of which is incorporated herein by reference. Such derivatized polyesters appeared promising in a number of areas, spurring firther research and development using the variety of such polyesters as well as other polyesters. As a result of further research, applicants have found as described herein that certain polyesters, functionalized polyesters, and their derivatives, when used with particular active ingredients can significantly and unexpectedly enhance the performance of such active ingredients.
U.S. Pat. No. 5,160,738 teaches a cosmetic composition which uses particular polyol fatty acid polyesters as an alternative to petrolatum for skin and hair products as occlusive agents. The compositions include a blend of two or more polyol fatty acid polyesters derived from aliphatic or aromatic polyols of at least 4 free hydroxyl groups, at least 60% of which are esterified with one or more fatty acids of from 8-22 carbon atoms.
U.S. Pat. No. 5,411,729 discloses polyester humectants for hair and skin for lubricating, softening and conditioning. The humectants are derived from esterification of hydroxyl-containing silicone compounds, diacid and polyhydroxy compounds.
Based on the foregoing, there is a need in the art for improved topical compositions with chemical exfoliating agents having decreased irritation and which provide improved and/or better controlled effects of such agents in cell renewal and desquamation. There is also a need for a composition which can maintain sunless tanning agents on the surface of the skin for a prolonged period, assist in color development and maintain a persistent color from use of these agents. There is further a need in the art for a composition having skin lightening agents and/or insect repellents such as DEET which can maintain these compositions on the surface of the skin and significantly enhance their effectiveness.